A Statistical Analysis of Density Perturbations in Relation to Solar X-Flare Events Isolated from Coronal Mass Ejections

The relationships between solar flares, the Earth’s Thermosphere, and the satellite’s orbiting our planet are of crucial importance for satellite operators to understand. The solar flare events in association with the Geomagnetic Halloween storm of 2003 have been studied in the past, however there has been a lack of research into the effects of solar flares without the accompaniment of Coronal Mass Ejections (CMEs). This paper details the investigation of the Thermosphere’s response to X-class solar flare events from 2002-2017, with a focus on the years 2002-2006. The Thermosphere density, derived from the on-board accelerometers of the Gravity Recovery and Climate Experiment (GRACE) twin satellites, and the CHallenging Minisatellite Payload (CHAMP) satellite, provide the information required to perform a statistical analysis on the effects of the solar flare events with respect to the Thermosphere density and the satellite’s attitude. It is proposed that the flux brought to the Earth by flares may have a large enough impact on the Earth’s Thermospheric density such that the drag perturbation induced on the orbiting satellites would increase. The presence of fluctuations in the density-derived data of the satellites, corresponding to the time of the flare events, is thought to be a result of the increased drag force causing visible and significant accelerometer fluctuations. Increasing drag force on satellites could then result in the need for in-orbit attitude adjustments, which could pose an increased risk in space-debris collision. A statistical analysis of the X-class events during the lifetimes of GRACE and CHAMP could provide insight to the probable increase of the Earth’s Thermospheric denisty due to the differing strengths of these flares. Such knowledge would be valuable to spacecraft operators entering a period of solar maximum, where an increase in solar activity is expected.

Utilizing NOAA’s online source of solar active events, the information from 115 X-class flares, starting on April 21^st, 2002 until September 10^th, 2017, were extracted for this study. The objective of this study is to provide a probability statement for satellite operators, to understand the effects of the increased density levels of the Thermosphere on orbiting satellites. Challenges that will be discussed include the variation of the flare location on the Sun, the accompaniment of partial and full-halo CME’s with the flare events, and the restrictions of GRACE and CHAMP data available for analysis.